<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>或</title>
</head>
<body>
    <script>
        var x=NaN,y=undefined,z=1,m=1,n='0',j=33,a=!(!undefined),b=10;
        console.log(x||y||z);
        console.log(m||n||j);
        console.log(a||b);

    </script>
</body>
</html>